An image forming apparatus has a storage such as an HDD (Hard Disk Drive) or SSD (Solid State Drive) to perform a printing process or scanning process through the storage. Therefore, if the storage is excessively accessed because of combined operation of printing and scanning or another reason, the speed of data transmission to the storage declines and as a consequence, the printing speed declines.
One technique to solve the above problem is that if the speed of data transmission to the storage does not meet the allowable speed, a warning is given to the user and upon receipt of the warning the user manually installs an additional storage to increase the speed of data transmission to the storage by striping with the additional storage (for example, see Patent Literature 1).